High energy density batteries have been produced which are rechargeable, light in weight (producing at least 50 watthours or more per pound) and made from readily available materials. Recently, various attempts have been made to improve the power:weight ratio, battery performance characteristics and dependability, so as to make such batteries suitable for use to power electric drive automobiles. High energy density batteries have been made utilizing zinc-chlorine and zinc-bromine systems and in some such batteries electrodes of graphite or porous carbon have been disclosed. Although such batteries have usefully generated electricity and have had fairly satisfactory power:weight ratios, problems have been encountered in their use. Contacting of the halogen with the positive electrode has often been unsatisfactory and power:weight ratios have not been as high as desired. Such disadvantages have been overcome to a significant extent by the present invention.